The fundamental equation for a pure substance is : S= aUV N bN3 UV With N the number of moles, a, b two positive constants and S, U, V entropy, internal energy and volume. Show that pressure p can be obtained from: p = b v3-avT With v = V/N. T is temperature. Hint: Differentiate the eq. for S wrt to U at constant V and wrt to V at constant U. Then compare the results with the equation : dU = Tds - pdV